I actually have thought about it and I'm going to do it right now it looks too clean to match with the rest of the bike.
Firstly I using green scotch pads to remove the shine from the chrome and give it a brushed aluminum look similar to the fork leader. As far as technique goes I found and old 2 inch paintbrush and chopped the hairs in half using my razor. I then started with a matte black base coat spray. I noticed it worked best when I sprayed directly on the brush. I then hit all the edges, outer curves, and bolts. Anywhere the bike would normally be scratched. The point is for it to look scratchy and beat up so just go to town brushing all those spots mentioned. Move the brush around as much as possible just get the paint on I used varying pressure from light strokes to just mashing the brush into the rails. Whatever works best.
Next I looked for a more uniform coat and I used rustoleum hammered finish in a sort of light bronze color. For this layer I sprayed directly onto the rails but do so sparingly you don't want a nice even coat. Just spray enough to where it covers most of the visible metal staying away as much as possible from the black spots. Then grab your same brush and move that paint around as much as possible. Do it quickly because if you wait for it to dry it'll be much harder and stickier. If that happens though just spray some on the brush and throw it on. again use varying brush strokes. I usually wait a couple minutes for the previous coats to dry as well.
Lastly get some dark red primer or similar color. I prefer primer because actual rust isn't glossy, lightly spray this onto the same brush. The colors dry fast so don't worry about mixing and if they do so what haha. Anyways this is your lightest coat so spray lightly onto your brush and hit and areas that would likely rust (bolts, straights on rails, curls) what have you. Get creative this technique will prove invaluable in the future and it'll only get better or "worse" as time passes. I didn't clear it because I like the look of the different textures and the varying gloss from The matte and gloss paints. Once it all said and done "finito" you have your old looking new seat.
I'll post progress pics into this thread as I paint my fork leader.